1. Field of the Invention
The present invention relates in general to a deck mechanism of a video cassette recorder having a jog shuttle function for achieving a desired speed change while continuing the contact of a pinch roller with a capstan shaft in the case of a mode conversion from a PLAY mode to a CUE mode or to a REV mode, and more particularly to a device for driving an idler of the deck mechanism, the idler transmitting a rotational force of the capstan shaft to either of a tape supply reel or a tape take-up reel.
2. Description of the Prior Art
With reference to FIG. 1, there is shown in a schematic plan view a conventional deck mechanism of a video cassette recorder (VCR) having the aforementioned jog shuttle function.
In this drawing, the reference numeral 1 denotes a rotary head drum, 2 and 3 denote a tape supply reel and a tape take-up reel, respectively, 4 and 5 denote a capstan shaft and a pinch roller, respectively, 6 denotes a gear pulley, 7 denotes a belt, 8 and 9 denote a F/R (fast forward/rewind) gear and an up/down gear, respectively, 10 denotes a clutch assembly, 11 denotes an idler or an idle gear, and 12 and 13 denote first and second connection gears, respectively.
In the conventional deck mechanism of the VCR having the jog shuttle function, movement of one frame picture in a direction of "CUE.fwdarw.REV" or movement of one frame picture in a direction of "REV.fwdarw.CUE", both movements being carried out using a jog dial (not shown), generally causes a picture noise.
If described in detail, the pinch roller 5 during the play mode closely contacts with the capstan shaft 4 which is rotated in the counterclockwise direction of FIG. 1, thus to cause the tape T to run in a direction shown at the arrow B of the drawing.
At this time, when the take-up reel 3 can not tightly and completely take up the tape T, this tape T may sag about a lower periphery of the rotary head drum 1 as shown at the dash and dot line of FIG. 1. This sag of the tape T about the head drum 1 results in the picture noise.
The capstan shaft 4 makes the tape T momentarily run in the direction of the arrow B' of FIG. 1 in practical use of the jog shuttle VCR as described above. However, in order to take up the tape T, the rotational force of the capstan shaft 4 should be transmitted to the take-up reel 3 in order of the capstan shaft 4.fwdarw.the belt 7.fwdarw.the gear pulley 6.fwdarw.the F/R gear 8.fwdarw.the clutch assembly 10.fwdarw.the up/down gear 9.fwdarw.the idle gear placed on the position 11'.fwdarw.the take-up reel 3. On the other hand, in order to rotate the supply reel 2 to take up the tape T thereby, the rotational force of the capstan shaft 4 should be transmitted to the supply reel 2 in order of the idle gear shifted from the dotted position 11'to the solid position 11.fwdarw.the first connection gear 12.fwdarw.the second connection gear 13.fwdarw.the supply reel 2. It is thus noted that there is a timing interval between the tape running by the capstan shaft 4 and the reel rotation since it is not until the rotational force of the capstan shaft 4 is transmitted to the take-up reel 3 or to the supply reel 2 that the reel is rotated. Such a timing interval causes the noise to appear on the picture.
One approach to prevent such a picture noise caused by the timing interval is to use an additional force other than the rotational force of the capstan shaft 4 to rotate the supply reel 2 or the take-up reel 3. A known structure for rotating reel 2 by the additional force is shown in FIGS. 2 to 4. As shown in FIGS. 2 and 3, the known supply reel drive structure includes a hinge pin 15 which is mounted on a lower surface of a base plate 14. A turning lever 16 having a gear section 16a is rotatably coupled to the hinge about pin 15. This turning lever 16 is biased counterclockwise about the pin 15 by a tension coil spring 17 and, at the same time, cooperates with a function plate 18. The gear section 16a of the turning lever 16 selectively gears, in cooperation with the function plate 18, into a lower gear 19 of the supply reel 2.
The gear section 16a of the turning lever 16 as well as the lower gear 19 of the supply reel 2 has a frictional clutch structure of the ratchet type and transmits the additional force in a unidirection, or in the counterclockwise direction of the lower gear 19.
In the drawings, the reference numerals 20 and 21 denote a felt and a compression coil spring, respectively.
In operation of the above supply reel drive structure, when the jog dial is rotated in "CUE.fwdarw.REV" direction in the play mode of the deck mechanism, a loading motor is rotated to make the deck mechanism achieve a REV-SLOW mode. At this time, the function plate 18 linearly moves in a direction shown at the arrow C of FIGS. 2 and 3.
The function plate 18, linearly moving in the direction of the arrow C, pushes the turning lever 16 such that this turning lever 16 turned clockwise about the hinge pin 15. In accordance with such a turning operation of the lever 16, the gear section 16a of the turning lever 16 forcibly rotates the lower gear 19 of the supply reel 2 counterclockwise Here, the felt 20 is tightly interposed between the lower gear 19 and the supply reel 2, so that the rotational force of the lower gear 19 is transmitted to the supply reel 2 through the felt 20 to rotate this supply reel 2, thus to cause the supply reel 2 to take up the tape T. At the same time, the clockwise rotation of the capstan shaft 4 causes the tape T to run in the direction of the arrow B'of FIG. 1. The idle gear 11 driven by the rotational force of the capstan shaft 4 is separated from the take-up reel 3 and gears into the first connection gear 12 and this makes the supply reel 2 rotate by the rotational force of the capstan shaft 4, thus achieving the desired REV-SLOW mode of the deck mechanism.
On the contrary, when the jog dial is rotated in the "REV.fwdarw.CUE" direction, the loading motor is rotated to make the deck mechanism achieve a CUE-SLOW mode. At this time, the function plate 18 linearly moves in a direction opposed to the direction of the arrow C. Such a movement of the function plate 18 causes the turning lever 16 to be free from the interference with the function plate 18, so that this turning lever 16 is turned counterclockwise about the hinge pin 15 due to the restoring force of the tension coil spring 17. The gear section 16a of the turning lever 16 is thus disengaged from the lower gear 19 of the supply reel 2.
At this time, the capstan shaft 4 is rotated in a counterclockwise direction to make the tape T run in the direction of the arrow B. The idle gear 11' connected to a capstan motor is separated from the first connection gear 12 and gears into the take-up reel 3 and this makes the take-up reel 3 rotate clockwise. Hence, the desired CUE-SLOW mode of the deck mechanism is achieved.
As described above, when the jog dial is rotated in the CUE.fwdarw.REV direction or in the REV.fwdarw.CUE direction, one frame picture moves in the reversed direction or in the forward direction.
However, in the deck mechanism having the above structure for rotating the supply reel by the additional force, the supply reel should have a two-stepped gear clutch type structure thus to result in 3 designing problem caused by a high height of the supply reel structure. Such a supply reel structure having the high height also causes an increase of manufacturing cost.
In addition, in order to make the supply reel 2 be not affected by additional force when the jog shuttle is rotated in the REV.fwdarw.CUE direction to achieve the CUE-SLOW mode of the deck mechanism, the lower gear 19 of the supply reel 2 as well as the gear section 16a of the turning lever 16 has the ratchet gear profile. However, in order to completely achieve the above object, it is required to catch the supply reel 2 by an additional brake and the clutch should generate a slip and, at the same time, the teeth of the ratchet gears of the lower gear 19 and of the gear section 16a should go wrong with each other. In this regard, the supply reel 2 is inevitably affected by the turning lever 16 which is rotated counterclockwise by the restoring force of the tension coil spring 17 to return to its initial position. Thus, when the jog shuttle is rotated in the REV.fwdarw.CUE direction to achieve the CUE-SLOW mode, the supply reel 2 supplies the tape T in advance and this causes a noise to momentarily appear on the picture.
Furthermore, the above deck mechanism introduces a difficulty caused by necessity of coincidence of the timing for starting the capstan motor with the timing for starting the loading motor, thus to be restricted from mass production. A continuous repeat of the CUE.fwdarw.REV operation and the REV.fwdarw.CUE operation causes increase of the tensile force of the tape T. Such an increase of the tensile force of the tape T results in excessively close contact of the tape T with the rotary head drum 1, thus to cause generation of the picture noise, increase of a sound noise, and damage of the tape T which results in deterioration of the picture quality.